I can't think of any gp gun i would want to use every single game. First i would get bored of it, then realize i have no gp left.

Maybe the people who don't buy NX get it...
But yeah, GP Perms are normally only sold during an event, the ACR was sold for permanent duration a few weeks ago for like 100k or something... so you just need to keep an eye on events and save up.